Additive manufacturing typically refers to the production of 3D metal articles via layer-by-layer deposition. A few methods for additive manufacturing of metallic glass 3D articles currently exist. Most of these methods involve melting of powders by means of a radiation beam.
One method uses a Laser Engineered Net Shaping (LENS) process (see for example B. Zheng, Y. Zhou, J. E. Smugeresky, and E. J Lavernia, “Processing and Behavior of Fe-Based Metallic Glass Components via Laser-Engineered Net Shaping”, Metallurgical and Materials Transactions 40A, 1235-1245 (2009), and V. K. Balla and A. Bandyopadhyay, “Laser Processing of Fe-based Bulk Amorphous Alloy”, Surface & Coatings Technology 205, 2661-2667 (2010), the references of which are incorporated herein in their entirety). In this approach, a flowing stream of metallic glass powder is deposited locally on a molten pool over a substrate created by a focused laser beam and metallurgically bonds to the substrate. Applying this approach point-by-point, line-by-line, and layer-by-layer, a 3D article may be built.
Another method uses a Selective Laser Melting (SLM) process (see for example U.S. Pat. No. 8,052,923, and G. Yang, X, Lin, F. Liu, Q. Hu, L. Ma, J. Li, and W. Huang, “Laser Solid Forming of Zr-Based Bulk Metallic Glass,” Intermetallics 22, 110-115 (2012) and S. Pauly, L. Lober, R. Petters, M. Stoica, S. Scudino, U. Kuhn and J. Eckert, “Processing Metallic Glasses by Selective Laser Melting,” Materials Today 16, 37-41 (2013), the references of which are incorporated herein in their entirety). In this approach, a powder layer, deposited on a substrate, is locally melted by a focused laser, and subsequently is locally rapidly solidified. Again, applying this approach point-by-point, line-by-line, and layer-by-layer, a 3D article may be built.
These approaches have several drawbacks. These include the use of fine powders that can introduce a plurality of bonding surfaces. Having multiple bonding surfaces in turn can promote porosity. Moreover, any oxide layers on the powder surfaces may inhibit bonding and can introduce oxide inclusions into the final article such that the final article may be prone to crystallization or cracking, thereby having diminished glass forming ability and mechanical performance. Another drawback is the use of radiation heating, which can promote uneven heating from particulate to particulate and may render the management of heat very inefficient.
U.S. Patent Publication Nos. 2013/0306198 and 2014/0202595 disclose additive manufacturing methods for metallic glasses based on layer-by-layer deposition, which involves successive deposition of an added liquid layer to a base metallic glass layer. Both applications involve methods where the added liquid layer is deposited as droplets (i.e. as a spray). Publication No. 2013/0306198 also mentions the possibility of the liquid layer being deposited as a continuous stream. In both applications, the methods include cooling each added layer sufficiently fast to form a metallic glass. However, the applications do not disclose how to promote wetting between the added liquid layer and base metallic glass layer, or how to avoid crystallization of the base metallic glass layer due to heating by conduction with the added liquid layer.
Developing an additive manufacturing method capable of producing 3D metallic glass articles with properties that are substantially similar to a monolithic material is of technological importance.